Updated 7:37 p.m. | Michigan Democratic Sen. Carl Levin announced Thursday that he will retire at the end of 2014.

The chairman of the Armed Services Committee, first elected in 1978, is the longest-serving senator in Michigan history and will turn 80 before Election Day next year.

In a statement, Levin said the decision not to seek another term was "extremely difficult."

"I love representing the people of Michigan in the U.S. Senate and fighting for the things that I believe are important to them," he said. "As Barbara and I struggled with the question of whether I should run again, we focused on our belief that our country is at a crossroads that will determine our economic health and security for decades to come. We decided that I can best serve my state and nation by concentrating in the next two years on the challenging issues before us that I am in a position to help address; in other words, by doing my job without the distraction of campaigning for re-election."

Levin would have been heavily favored to win another term heading into 2014. The six-term senator has not faced a tough contest in almost three decades: He has won with at least 57 percent of the vote since his first re-election in 1984.

It's unlikely — but not impossible — that the race for Levin's successor will be competitive. In 2012, President Barack Obama won the Wolverine State by 9 points. In fact, a GOP presidential nominee has not won Michigan since 1988, and the state has only elected one Republican — former Sen. Spencer Abraham in 1994 — to a single term since 1972.

Contenders from both parties could come from the House: Rep. Gary Peters, a Democrat, has said he's keeping his options open for 2014, and Michigan Republicans said Rep. Justin Amash is eyeing the seat.

Democrats also named Jocelyn Benson, nominee for secretary of state in 2010, and former Rep. Mark Schauer as potential candidates. State Senate Minority Leader Gretchen Whitmer could also consider a bid, though she announced earlier this year that she would not run for governor because of family considerations.

An attorney by trade, Levin worked for the Michigan Civil Rights Commission in the 1960s. He was elected to the Detroit City Council in 1969, where he served for eight years before running for Senate. In 1978, Levin defeated Republican Sen. Robert Griffin by 4 points.

Update 7:37 p.m.

Republicans on the ground stress that in non-presidential cycles, their candidates do well in statewide campaigns. Democrats admit that the seat is more competitive without Levin, but are bullish — especially if the GOP produces a tea party candidate. "We fully expect to keep Michigan blue in November 2014,” Democratic Senatorial Campaign Committee Chairman Michael Bennet of Colorado said in a statement.

Republicans were already abuzz with prospects as word of Levin's announcement spread. Reps. Mike Rogers and Candice S. Miller are likely to look at the race. Both have been mentioned before as statewide candidates, and President George W. Bush encouraged Miller to challenge Sen. Debbie Stabenow in 2006.

At least one name from outside the GOP congressional delegation is being floated as well: Lt. Gov. Brian Calley. But one state operative hypothesized that Calley would run for Amash's House seat if the congressman runs for Senate.

One possible candidate wasted no time in taking his name out of contention. A spokesman for state Attorney General Bill Schuette, a Republican, issued a statement late Thursday saying he wasn't interested in running.

"Republicans can win in Michigan, as the Governor, Lt. Governor, Secretary of State, and Attorney General have proven," National Republican Senatorial Committee spokesman Brad Dayspring said in a statement. "That is why we've been speaking to local officials and grassroots organizations in preparation for Senator Levin's potential retirement, and now that groundwork will start to pay off."